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Questions and Answers
Tetanus results in a sustained muscle contraction due to a decrease in intracellular calcium levels.
Tetanus results in a sustained muscle contraction due to a decrease in intracellular calcium levels.
False
Motor units consist of a single α motor neurone and all the muscle fibers it innervates.
Motor units consist of a single α motor neurone and all the muscle fibers it innervates.
True
During sustained muscle contraction, all motor units are always active to prevent fatigue.
During sustained muscle contraction, all motor units are always active to prevent fatigue.
False
The optimal resting length of a sarcomere allows for maximum strength of contraction.
The optimal resting length of a sarcomere allows for maximum strength of contraction.
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Recruitment of motor units allows for graded increases in force during muscle contraction.
Recruitment of motor units allows for graded increases in force during muscle contraction.
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Tetanus occurs only at low levels of stimulation and requires minimal action potentials.
Tetanus occurs only at low levels of stimulation and requires minimal action potentials.
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As muscle length increases, tension developed increases indefinitely.
As muscle length increases, tension developed increases indefinitely.
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Smaller motor units are typically recruited last during muscle contractions requiring increased strength.
Smaller motor units are typically recruited last during muscle contractions requiring increased strength.
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The mechanism of contraction for smooth muscle is fundamentally different from that of cardiac muscle.
The mechanism of contraction for smooth muscle is fundamentally different from that of cardiac muscle.
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A simple muscle twitch involves a contraction followed by sustained tension.
A simple muscle twitch involves a contraction followed by sustained tension.
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Study Notes
Muscle Components
- Remember the individual components of a muscle fiber.
Muscle Fiber Length and Force
- The force a muscle generates when it contracts is related to its resting length.
- There is an optimal resting length for a sarcomere to achieve maximum strength of contraction.
- The "Length-Tension Curve" illustrates this relationship:
- As muscle length increases, tension also increases up to a limit.
- An overstretched sarcomere with no overlap between actin and myosin results in minimal force generation.
Muscle Contraction Strength
- Two factors can alter the force/strength of skeletal muscle contraction:
- Tetanus/Tetany
- Recruitment of Motor Units
Muscle Twitch
- A simple muscle twitch consists of a contraction followed by relaxation.
Tetanus in Skeletal Muscle
- Tetanus/Tetany is a sustained muscle contraction.
- At high levels of stimulation, repeated action potentials lead to a sustained rise in intracellular calcium.
- This sustained increase in calcium allows for greater contraction force than a single twitch.
Motor Units
- A motor unit consists of a single alpha motor neuron and all the muscle fibers it innervates.
- Motor units vary in size:
- Larger motor units provide less precise control.
- Smaller motor units provide fine control and are recruited first for smaller movements.
- To increase force, more motor units are recruited.
- During prolonged activity, motor units rotate so that some are contracting while others rest, delaying fatigue.
Cardiac Muscle Action Potential
- The cardiac muscle action potential is crucial for muscle contraction.
Cardiac Muscle Contraction Mechanism
- The mechanism of contraction in cardiac muscle involves a sequence of events triggered by the action potential, including calcium release and the sliding filament mechanism.
Smooth Muscle Contraction Mechanism
- Smooth muscle contraction operates via a different mechanism involving calcium signaling, but without striations or sarcomeres.
Muscle Types: Key Differences
- Smooth, cardiac, and skeletal muscles differ in:
- Structure
- Contraction mechanism
- Control
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Description
Test your knowledge on muscle components, length-tension relationships, and factors affecting muscle contraction strength. This quiz covers essential concepts about muscle fibers, contraction mechanisms, and the effects of tetanus and motor unit recruitment.
